1. Field of the Invention
The present invention relates to a fuel pressure regulator for use in a fuel injection system for an internal combustion engine in which a liquid fuel is supplied under pressure through a main fuel conduit and through fuel injectors into the engine.
2. Description of the Prior Art
In a conventional fuel injection system for an internal combustion engine, a liquid fuel is pumped by an electrically operated constant-delivery type fuel pump and flows through a main fuel conduit to which are connected a plurality of branch conduits which respectively terminate in electro-magnetically operated fuel injectors mounted on the engine. In general, the fuel pump is designed to discharge the fuel at a rate which is from 2 to 3 times of the fuel consumption rate of the engine.
The fuel injection system has a fuel pressure regulator disposed in the main fuel conduit at its downstream end, i.e., downstream of the connections between the main fuel conduit and the branch conduits. Because of the large capacity of the fuel pump as compared with the actual fuel consumption rate of the associated engine, the fuel pressure regulator is required to deal with a return flow of the fuel at a very high rate and, thus, is inevitably large-sized and of a heavy weight.
In addition, the fuel pressure regulator is also required not only to maintain the fuel pressure in the main fuel conduit at a substantially constant pressure level irrespective of any change in the rate of the fuel flow therethrough, but also to ensure that the fuel residual or left in the main fuel conduit after the fuel pump is stopped is kept at a certain pressure level. So as to comply with the second requirement, the fuel pressure regulator must be provided with a valve consisting of valve members which have been precisely worked and precisely assembled, which results in an increase in the cost of manufacture of the fuel pressure regulator.